Consider the single factor APT. Portfolio A has a beta of 1.09 and an expected return of 22%. Portfolio B has a beta of .98 and an expected return of 13%. The risk-free rate of return is 2.85%. If you wanted to take advantage of an arbitrage opportunity, you should take a short position in portfolio and a long position in portfolio because portfolio A provides risk premium of and portfolio B provides risk premium of which should converge under no-arbitrage condition